Magnetic Fields Control Liquid Crystals’ Optical Properties

RIVERSIDE, Calif., June 27, 2014 — A new technique that forms and controls magnetically responsive liquid crystals could be applied to many types of displays.

Conventional liquid crystals, often used in electronic displays, are composed of tiny rod-like molecules. Researchers at the University of California, Riverside, have created crystal nanorods that rotate and realign themselves parallel to nearby magnetic fields.

This illustration shows magnetic control over light transmittance in the liquid crystals. “B” represents the alternating magnetic field. Images courtesy of UC Riverside.
“We utilized our expertise in colloidal nanostructure synthesis to produce magnetite nanorods that can form liquid crystals and respond strongly to even very weak magnetic fields,” said lead researchers Dr. Yadong Yin, an associate professor of chemistry at the university. “Even a fridge magnet can operate our liquid crystals.”

The nanorods can also form patterns to control the transmittance of polarized light in selected areas.

The polarization-modulated pattern changes the brightness and darkness by rotating in the direction of the cross polarizers.
“Such a thin film does not display visual information under normal light, but shows high contrast patterns under polarized light,” Yin said, noting that this is not possible with commercial liquid crystals.

The new liquid crystals could be used in applications such as signs and displays, optical modulation and anti-counterfeiting efforts, the researchers said.

The work was funded by grants from the National Science Foundation and the U.S. Army Research Laboratory. The research was published in Nano Letters (doi: 10.1021/nl501302s).